A printing method has been put into practice in which a printing ink is fed onto the printing face constituted by the outer surface of a printing cylinder of a cylindrical shape (hereinafter simply referred to as printing cylinder), the printing cylinder is set to a printing press and is rotated in order to print the papers, as is done, for example, in gravure printing.
In the above-mentioned printing method using the printing cylinder, the ink adhering to the printing face of the printing cylinder is wiped off after the printing is finished. The ink layer adhering to the side surfaces of the printing cylinder usually becomes as thick as ten and several millimeters at a moment when the printing is finished. The ink adhering to the side surfaces of the printing cylinder cannot be automatically removed because the printing cylinder is heavy and that the ink is not adhered uniformly. If the ink that is adhered is not wiped off, then it mixes into the ink used in the next printing, causing the ink to lose its color tone. Furthermore, the ink that is coagulated peels off at the time of printing and adheres to the surface of the printing cylinder causing the doctor blade to be damaged and hindering the printing.
In order to solve the problem caused by the ink that is adhered to the side surfaces of the printing cylinder, a method has been disclosed in Japanese Laid-Open Patent Publication No. 91281/1987 in which the printing cylinder is removed from the printing press and the side surfaces thereof are cleaned. That is, the printing cylinder having ink adhered to the side surfaces thereof is removed from the printing press, and the water is sprayed under very high pressure against the printing cylinder.
According to the above method, however, it is necessary to clean the side surfaces of the printing cylinder in addition to the operation for wiping the ink off the printing face of the printing cylinder that is removed from the printing press; i.e., a great deal of labor is required to move the very heavy printing cylinder to the cleaning device which sprays water under a very high pressure. Moreover, there is a likelihood of damaging the printing face of the printing cylinder while it is being moved or during the operation for washing out the ink.
Japanese Utility Model Laid-Open Publication No. 93236/1986 proposes a printing cylinder which prevents the ink from adhering onto the side surfaces by providing the side surfaces of the printing cylinder with a layer of a fluorine-resin such as polytetrafluoroethylene. This makes it possible to considerably reduce the amount of ink adhering to the side surfaces of the printing cylinder making, however, it necessary to remove the ink adhered to the side surfaces in addition to the operation for wiping the ink off the printing face of the printing cylinder. Like the above-mentioned method, therefore, it is necessary to clean the side surfaces of the printing cylinder leaving such problems as the introduction of a cleaning step and the likelihood of damaging the printing cylinder while it is being moved for the purpose of being cleaned.